1. Field of the Invention
The present invention relates to a method of and an apparatus for developing an exposed photoresist coated on the surface of a silicon wafer, with a developing liquid, a development control apparatus for controlling various components of a developing apparatus, and an information storage medium which stores, as software, a program for enabling a computer to perform various processing operations.
2. Description of the Related Art
At present, fine interconnection patterns of semiconductor circuit devices are formed by photolithography. According to the photolithographic process, it is necessary to develop an exposed photoresist coated on the surface of a silicon wafer with a developing liquid by a developing apparatus.
One conventional developing apparatus will be described below with reference to FIGS. 1a, 1b through 5 of the accompanying drawings. The conventional developing apparatus, denoted by 100, processes silicon wafer 101 with a photoresist coated on its surface. As shown in FIG. 4a, developing apparatus 100 has wafer chuck mechanism 102 as a wafer holding means. Wafer chuck mechanism 102 is mounted on the upper end of rotatable shaft 103 which extends vertically. Silicon wafer 101 is detachably held by wafer chuck mechanism 102 such that the surface coated with the photoresist lies horizontally and faces upwardly.
Rotatable shaft 103 with wafer chuck mechanism 102 mounted on its upper end is rotatably supported by wafer rotating mechanism 104 (see FIG. 3) as a wafer rotating means which comprises a drive motor or the like. Wafer rotating mechanism 104 rotates silicon wafer 101 supported by wafer chuck mechanism 102 in a horizontal plane.
As shown in FIG. 3, developing apparatus 100 also has developing liquid supply mechanism 105 as a developing liquid supply means which comprises a tank and a pump, and cleaning liquid supply mechanism 106 as a cleaning liquid supply means which comprises a tank and a pump. Developing liquid supply mechanism 105 supplies developing liquid 107 comprising an aqueous alkaline liquid to the surface of silicon wafer 101 held by wafer chuck mechanism 102. Cleaning liquid supply mechanism 106 supplies pure water 108 as a cleaning liquid. Developing liquid supply mechanism 105 has developing nozzle 109, and cleaning liquid supply mechanism 106 has cleaning nozzle 110. Developing nozzle 109 and cleaning nozzle 110 are movably supported by nozzle moving mechanism 111. As shown in FIGS. 1a through 2b, nozzle moving mechanism 111 moves developing nozzle 109 and cleaning nozzle 110 between a position which faces the surface of silicon wafer 101 held by wafer chuck mechanism 102 and a position retracted away from the surface of silicon wafer 101.
Developing nozzle 109 has a slit structure capable of supplying a screen of developing liquid 107 diametrically across silicon wafer 101, which is of a disk shape, at the center of silicon wafer 101. Cleaning nozzle 110 comprises a slender pipe capable of supplying pure water 108 to a central position on silicon wafer 101.
As shown in FIG. 3, wafer rotating mechanism 104, developing liquid supply mechanism 105, cleaning liquid supply mechanism 106, and nozzle moving mechanism 111 are connected to operation control apparatus 112 comprising a computer as a development control apparatus. A control program for controlling a developing process is installed in operation control apparatus 112. Based on the installed control program, operation control apparatus 112 controls operation of the above mechanisms 104, 105, 106, 111 to perform the developing process.
Developing apparatus 100 can develop an exposed photoresist coated on the surface of the silicon wafer 101 with developing liquid 107 supplied thereto. Supplied developing liquid can be washed away from the surface of the silicon wafer 101 by pure water 108.
More specifically, as shown in FIG. 4a, silicon wafer 101 whose surface is coated with a photoresist is horizontally held by wafer chuck mechanism 102. Then, as shown in FIG. 5, silicon wafer 101 held by wafer chuck mechanism 102 is rotated at a high speed by wafer rotating mechanism 104.
In a period {circle around (1)} shown in FIG. 5, developing nozzle 109 of developing liquid supply mechanism 105 is moved to a position facing the surface of silicon wafer 101 by nozzle moving mechanism 111. Thereafter, as shown in FIG. 4b, in a period {circle around (2)} shown in FIG. 5, developing liquid supply mechanism 105 supplies developing liquid 107 to the surface of silicon wafer 101 which is being rotated at a high speed.
While developing liquid 107 is being supplied to the surface of silicon wafer 101, the rotation of silicon wafer 101 is gradually decelerated to a predetermined speed, after which the supply of developing liquid 107 is stopped. As shown in FIG. 4c, a puddle of developing liquid 107 is now formed on the surface of silicon wafer 101. In a period {circle around (3)} shown in FIG. 5, the puddle of developing liquid 107 is maintained on the surface of silicon wafer 101 to develop the exposed photoresist.
Developing nozzle 109 is moved to the position away from the surface of silicon wafer 101 by nozzle moving mechanism 111. At the same time, cleaning nozzle 110 of cleaning liquid supply mechanism 106 is moved to the position facing the surface of silicon wafer 101 by nozzle moving mechanism 111.
After a predetermined developing time has elapsed, silicon wafer 101 is rotated at a high speed. As shown in FIG. 4d, in a period {circle around (4)} shown in FIG. 5, pure water 108 is supplied to the surface of silicon wafer 101 which is being rotated at a high speed. Supplied pure water 108 cleans the surface of silicon wafer 101, removing developing liquid 107 from the surface of silicon wafer 101.
The supply of pure water 108 is stopped after elapse of a certain time. As shown in FIG. 4e, in a period {circle around (5)} shown in FIG. 5, silicon wafer 101 is continuously rotated at a high speed even after the supply of pure water 108 is stopped, drying the surface of silicon wafer 101 with air.
In illustrated conventional developing apparatus 100, developing nozzle 109 and cleaning nozzle 110 are supported by nozzle moving mechanism 111 for movement between the position facing the surface of silicon wafer 101 and the position retracted away from the surface of silicon wafer 101. However, as shown in FIGS. 6a and 6b, another conventional developing apparatus 200 has developing nozzle 109 and cleaning nozzle 110 which are oriented toward the center of silicon wafer 101.
With conventional developing apparatus 200, it is not possible to eject pure water 108 vertically from cleaning nozzle 110 to the surface of silicon wafer 101. However, since it is not necessary to move developing nozzle 109 and cleaning nozzle 110 to the overlapping position, developing nozzle 109 and cleaning nozzle 110 do not need to be replaced with each other.
Therefore, a developing process can quickly be completed as developing nozzle 109 and cleaning nozzle 110 are not required to move in the developing process. However, even in this case, developing nozzle 109 and cleaning nozzle 110 are moved for the replacement of silicon wafer 101.
With conventional developing apparatus 100, 200, the exposed photoresist coated on the surface of silicon wafer 101 can be developed with developing liquid 107, and developing liquid 107 can be washed away from the surface of silicon wafer 101 with pure water 108.
However, actual developing processes performed on silicon wafer 101 by conventional developing apparatus 100, 200 have resulted in many developing defects. Attempts that have been made to find out causes of such developing defects have revealed that when developing liquid 107 is supplied to the surface of silicon wafer 101 that is rotating at a high speed, mist 120 is produced and contaminates developing nozzle 109, as shown in FIG. 4b. 
Mist 120 is composed of the developing liquid containing particles of the photoresist. If mist 120 is deposited on developing nozzle 109 and supplied together with developing liquid 107 in the process of developing an exposed photoresist on next silicon wafer 101, then a developing failure tends to occur oh a resist pattern on silicon wafer 101.
In recent years, efforts are being made to increase the diameter of silicon wafer 101 and make resist patterns finer. In view of such efforts, there is a tendency to use a longer developing nozzle 109 to apply developing liquid 107 uniformly to the surface of silicon wafer 101 at a high speed. Therefore, developing nozzle 109 necessarily has an increased area contaminated by mist 120 and hence is liable to cause a greater developing failure on the resist pattern on silicon wafer 101.
It is therefore an object of the present invention to provide a method of and an apparatus for developing an exposed photoresist coated on the surface of a silicon wafer without causing a developing failure, a development control apparatus for controlling various components of a developing apparatus without causing a developing failure, and an information storage medium which stores, as software, a program for enabling a computer to perform various processing operations without causing a developing failure.
According to an aspect of the present invention, there is provided a method of developing an exposed photoresist coated on a surface of a silicon wafer with a developing liquid. In this method, a cleaning liquid is supplied to the surface of the silicon wafer held by wafer holding means to form a puddle of the cleaning liquid before a developing liquid is supplied to the surface of the silicon wafer. Thereafter, the silicon wafer with the puddle of the cleaning liquid formed thereon is rotated in a horizontal plane, and the developing liquid is supplied to the surface of the silicon wafer.
Therefore, the developing liquid is supplied to the surface of the silicon wafer with the puddle of the cleaning liquid formed thereon. An impurity produced by a mist deposited on a developing nozzle and supplied with the developing liquid is suspended in the puddle of the cleaning liquid, and is not attached to the surface of the silicon wafer. Therefore, no developing failure occurs on a resist pattern of a photoresist on the surface of the silicon wafer, and the photoresist can well be developed to manufacture semiconductor integrated circuits with an increased yield.
According to another aspect of the present invention, there is also provided a method of developing an exposed photoresist coated on a surface of a silicon wafer with a developing liquid. In this method, before a developing liquid is supplied from developing liquid supply means to a surface of a silicon wafer held by wafer holding means, the silicon wafer is rotated by wafer rotating means, and a cleaning liquid is supplied from cleaning liquid supply means to the surface of the silicon wafer. Then, the developing liquid is supplied from the developing liquid supply means to the surface of the silicon wafer which is being supplied with the cleaning liquid while the silicon wafer is being rotated.
In the above method, the developing liquid is supplied to the surface of the silicon wafer which is being supplied with the cleaning liquid. An impurity contained in the developing liquid is suspended in the cleaning liquid that is being supplied, and is prevented from being attached to the surface of the silicon wafer.
According to still another aspect of the present invention, there is provided an apparatus for developing an exposed photoresist coated on a surface of a silicon wafer with a developing liquid, comprising wafer holding means, wafer rotating means, developing liquid supply means, cleaning liquid supply means, cleaning control means, and development control means. The wafer holding means holds the silicon wafer horizontally such that the surface coated with the photoresist faces upwardly. The wafer rotating means rotates the silicon wafer held by the wafer holding means in a horizontal plane. The developing liquid supply means supplies a developing liquid to the surface of the silicon wafer held by the wafer holding means. The cleaning liquid supply means supplies a cleaning liquid to the surface of the silicon wafer held by the wafer holding means. The cleaning control means and the development control means control the developing liquid supply means, the cleaning liquid supply means, and the wafer rotating means.
Specifically, the cleaning control means controls the cleaning liquid supply means to supply the cleaning liquid to form a puddle of the cleaning liquid on the surface of the silicon wafer before the developing liquid is supplied from the developing liquid supply means to the surface of the silicon wafer held by the wafer holding means. The development control means controls the wafer rotating means to start rotating the silicon wafer and controlling the developing liquid supply means to start supplying the developing liquid after the puddle of the cleaning liquid is formed on the surface of the silicon wafer by the cleaning control means. Therefore, the developing liquid is supplied to the surface of the silicon wafer with the puddle of the cleaning liquid formed thereon.
According to yet another aspect of the present invention, there is also provided an apparatus for developing an exposed photoresist coated on a surface of a silicon wafer with a developing liquid. In this apparatus, the cleaning control means and the development control means control the developing liquid supply means, the cleaning liquid supply means, and the wafer rotating means in a manner different from the pattern described above. Specifically, the cleaning control means controls the wafer rotating means to rotate the silicon wafer held by the wafer holding means and controlling the cleaning liquid supply means to supply the cleaning liquid to the surface of the silicon wafer before the developing liquid is supplied from the developing liquid supply means to the surface of the silicon wafer. The development control means controls the developing liquid supply means to supply the developing liquid to the surface of the silicon wafer which is being supplied with the cleaning liquid while the silicon wafer is being rotated by the cleaning control means. Therefore, the developing liquid is supplied to the surface of the silicon which is being supplied with the cleaning liquid.
In the above apparatus, the cleaning control means stops supplying the cleaning liquid after the developing liquid starts being supplied, and the development control means ends supplying the developing liquid after stopping supplying the cleaning liquid. Specifically, the surface of the silicon wafer is supplied with both the cleaning liquid and the developing liquid. Then, the supply of the cleaning liquid is stopped. Thereafter, the supply of the developing liquid is stopped. Consequently, the photoresist on the surface of the silicon wafer is well developed by the developing liquid that is eventually supplied solely.
The apparatus also has wafer cleaning means for controlling the cleaning liquid supply means to supply the cleaning liquid to the surface of the silicon wafer after the photoresist thereon is developed. The developing liquid on the surface of the silicon wafer after the photoresist thereon is developed is removed by the cleaning liquid supplied from the cleaning liquid supply means. Thus, means for supplying the cleaning liquid to the silicon wafer before the developing liquid is supplied is also used as means for supplying the cleaning liquid to remove the developing liquid. It is therefore possible to provide a developing apparatus which is simple in structure and capable of preventing exposure defects, without the need for adding dedicated hardware.
The apparatus further has developing liquid deaerating means for deaerating the developing liquid supplied to the surface of the silicon wafer. Since the developing liquid supplied to the surface of the silicon wafer is deaerated by the developing liquid deaerating means, a developing liquid containing air bubbles is not supplied to the surface of the silicon wafer.
A development control apparatus according to the present invention is provided in the above developing apparatus for controlling operation of the wafer holding means, the wafer rotating means, the cleaning liquid supply means, and the developing liquid supply means.
According to an aspect of the present invention, the development control apparatus has cleaning control means and development control means. The cleaning control means controls the cleaning liquid supply means to supply the cleaning liquid to form a puddle of the cleaning liquid on the surface of the silicon wafer before the developing liquid is supplied from the developing liquid supply means to the surface of the silicon wafer held by the wafer holding means. The development control means controls the wafer rotating means to start rotating the silicon wafer and controlling the developing liquid supply means to start supplying the developing liquid after the puddle of the cleaning liquid is formed on the surface of the silicon wafer by the cleaning control means.
According to another aspect of the present invention, the development control apparatus controls the developing liquid supply means, the cleaning liquid supply means, and the wafer rotating means in a manner different from the above pattern. Specifically, the cleaning control means controls the wafer rotating means to rotate the silicon wafer held by the wafer holding means and controlling the cleaning liquid supply means to supply the cleaning liquid to the surface of the silicon wafer before the developing liquid is supplied from the developing liquid supply means to the surface of the silicon wafer. The development control means controls the developing liquid supply means to supply the developing liquid to the surface of the silicon wafer which is being supplied with the cleaning liquid while the silicon wafer is being rotated by the cleaning control means.
The various means referred to in the present invention may be arranged to operate depending on their functions. These means may be implemented by dedicated hardware that operates depending on the functions, a computer that operates depending on the functions according to a program, a program for enabling a computer to operate depending on the functions, or a combination thereof.
An information storage medium according to the present invention stores a program for controlling operation of the wafer holding means, the wafer rotating means, the cleaning liquid supply means, and the developing liquid supply means in the above developing apparatus.
According to an aspect of the present invention, the information storage medium stores a program which enables a computer to perform a process including the steps of controlling the cleaning liquid supply means to supply the cleaning liquid to form a puddle of the cleaning liquid on the surface of the silicon wafer before the developing liquid is supplied from the developing liquid supply means to the surface of the silicon wafer held by the wafer holding means, and controlling the wafer rotating means to start rotating the silicon wafer and controlling the developing liquid supply means to start supplying the developing liquid after the puddle of the cleaning liquid is formed on the surface of the silicon wafer by the cleaning control means.
According to another aspect of the present invention, the information storage medium stores a program which enables a computer to perform a process including the steps of controlling the wafer rotating means to rotate the silicon wafer held by the wafer holding means and controlling the cleaning liquid supply means to supply the cleaning liquid to the surface of the silicon wafer before the developing liquid is supplied from the developing liquid supply means to the surface of the silicon wafer, and controlling the developing liquid supply means to supply the developing liquid to the surface of the silicon wafer which is being supplied with the cleaning liquid while the silicon wafer is being rotated by the cleaning control means.